The 6.5mm Grendel (6.5×39mm) is an intermediate cartridge designed by Arne Brennan, Bill Alexander and Janne Pohjoispää as a low recoil, high accuracy, 200-800 yard cartridge specifically for the AR-15 platform. It is an improved variation of the 6.5mm PPC. Since its introduction it has proven to be a versatile design and is now expanding out into other platforms including bolt-action rifles and the Kalashnikov system.
The name "6.5mm Grendel" was a trademark owned by Alexander Arms until it was legally released to allow the cartridge to become SAAMI standardized. The release of the trademark removes the requirement of manufacturers to seek the permission of the trademark holder to use the mark.
Development and history
The 6.5mm Grendel design goal was to create an effective 200-800 yard AR-15 magazine length loaded cartridge for the AR-15 platform that surpassed the performance of the native 5.56 NATO / 223 Remington cartridge. Constrained by the length of the 5.56 mm NATO round, the Grendel designers decided to use a shorter, larger diameter case for higher powder volume while allowing space for long, streamlined, high ballistic coefficient (BC) bullets. Firing factory loaded ammunition loaded with bullets ranging from 90 to 129 grains (5.8-8.4 g), its muzzle velocity ranges from 2,500 ft/s (760 m/s) with 129- and 130-grain (8.4 g) bullets to 2,900 ft/s (880 m/s) with 90 gr (5.8 g) bullets (similar in velocity to a 5.56 mm 77-grain (5.0 g) round).
The case head diameter of the Grendel is the same as that of the parent case the .220 Russian, the 7.62×39mm, and PPC cases. This is larger than the 5.56×45mm NATO, thereby necessitating the use of a non-standard AR-15 bolt. The increased case diameter results in a small reduction in the capacity of standard size M16/AR-15 magazines. A Grendel magazine with the same dimensions as a STANAG 30-round 5.56 magazine will hold 26 rounds of 6.5mm ammunition.Timeline
Proponents assert that the Grendel is a middle ground between the 5.56×45mm NATO and the 7.62×51mm NATO. It retains greater terminal energy at extended ranges than either of these cartridges due to its higher ballistic coefficient.
The 123 gr (8.0 g) 6.5 Grendel has more energy and better armor penetration at 1,000 meters than the larger and heavier 147 gr (9.5 g) M80 7.62 NATO round due to its longer low-drag bullet being more aerodynamic.
While the round has impressive performance, it is not without shortfalls. Better ballistics than the 7.62×51mm cartridge require the use of a long barrel and heavy bullet. To achieve the same results from shorter length barrels, even heavier bullets would be needed. Because it was made to fit the dimensions of an AR-15 rifle, its performance in comparison to other 6.5 mm rounds (.260 Remington, 6.5mm Creedmoor) falls short. Grendel cases cannot hold heavy bullets (123 gr compared to around 140 gr) and rapidly drop at a range of 1,200 yd (1,097 m), where others would remain effective. In comparison to the 5.56×45mm, it has a larger case diameter and reduced magazine capacity.
As noted above, the Grendel case is very closely related to the .220 Russian case. When sufficient load data was made available, a thorough study of the Grendel case, which constitutes a precisely dimensioned combustion chamber when the round is chambered, was done with the following results. In general, each additional grain of bullet weight will reduce muzzle velocity by 10 ft/s (47 m/s for each gram) and each additional inch of barrel length will increase muzzle velocity by 20 ft/s (2.4 m/s for each centimeter). Therefore, a handy rule of thumb is "one inch of barrel length equals two grains of bullet weight".
The 6.5mm Grendel is effective in the humane harvest of medium sized game.
The cartridge developer, Bill Alexander, has been quoted as saying he was looking for a cartridge with "more legs" (i.e. longer effective range) than the .50 Beowulf so that it could be used for white tail deer hunting. Its original marketing for military and police usage created skepticism about its suitability for hunting. Despite this, there has been critical acknowledgement that it is sufficient for CXP2 class game such as deer. Its manufacturer is more enthusiastic, saying that it has "flat trajectories and bullets well-suited to deer and varmints". It is similar to deer cartridges such as the .30-30 Winchester, .257 Roberts and .243 Winchester but is not in the same class as the .270 Winchester or the 30-06.
Copyright © 2014 F1 Engineering, All Rights Reserved.